docs: def list_structures(filename, treename=None):
      """Get a dictionary mapping branch names to leaf structures.
  
      .. warning:: ``list_structures`` is deprecated and will be removed in
         release 5.0.0.
  
      Parameters
      ----------
      filename : str
          Path to ROOT file.
      treename : str, optional (default=None)
          Name of tree in the ROOT file
          (optional if the ROOT file has only one tree).
  
      Returns
      -------
      structures : OrderedDict
          An ordered dictionary mapping branch names to leaf structures.
  
      """
      warnings.warn("list_structures is deprecated and will be "
                    "removed in 5.0.0.", DeprecationWarning)
      return _librootnumpy.list_structures(filename, treename)